UHM-DHM-SF-1H
43
Service Facts
User Interface
shows a
HIGH LIMIT?
User Interface
shows a
AUX LIMIT?
(reverse flow)
Scroll through
User Interface to
View number 1 of
Last 4 Faults
Cycle power to
furnace and call
for heat
Ignition occurs and
FAN ON delay
begins
Does fan come
on after ~45
seconds?
Does blower
wheel turn
freely?
Disconnect
electrical power to
furnace
YES
Check set screw
position and motor
bearings. Correct
or replace as
needed.
Check operation
NO
Is 120 vac
measured at motor
(5 pin connector
terminals 4 and 5)?
NO
YES
Is 120 vac
measured at 9
pin motor
harness
connector?
NO
NO
YES
Replace furnace control
Check operation
Replace wiring
harness.
Check operation
Are filter &
blower wheel
clean?
YES
Replace filter and
clean blower
wheel.
Check operation
NO
Is external
static pressure
greater than
nameplate?
YES
Correct application
or duct issues.
Check operation
YES
Is heat rise
within
specification?
See Service
Facts
NO
See serial motor checkout in
Service Facts or on 10 Flash
LED section.
Replace if needed
Is return air
temperature
above 85 F?
NO
Return air
temperature is
above max limit.
YES
Check for loose
insulation or other
objects within
furnace air stream
NO
Is outlet
manifold gas
pressure within
specifications?
YES
Correct gas
pressure
Check operation
NO
Is temperature at
high limit above
the switch setting?
See NOTE
YES
Replace high limit
switch
NO
YES
Disconnect
electrical power to
furnace
Does blower
wheel turn
freely?
NO
Check set screw
position and motor
bearings. Correct
or replace as
needed.
Check operation
Cycle power to
furnace and call
for heat
YES
Does fan come
on after ~45
seconds?
Ignition occurs and
FAN ON delay
begins
YES
Does motor
continue to run
during the
entire heating
cycle?
Is temperature at auxilary
limit switch above
specifications after heat
fan off delay ends?
YES
Replace auxiliary
limit switch
NO
Check for excessive
reverse flow during an off
cycle
YES
DEFINITION:
Limit switches are safety
devices that will open
when an abnormal high
temperature has been
sensed.
REMOVE ALL JUMPER
WIRING TO SWITCHES!
Under no circumstances,
shall these switches be
left jumpered when not
troubleshooting.
NOTE: Make sure any
temperature measuring
devices (thermocouples, dial
thermometers) used to
estimate limit temperature
are within ¼ inch of limit
measurement point
NO
See next page for
additional 4 flash
faults
4 Flash Fault LED
NO
Summary of Contents for ADHMB060BCV3VA
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